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Browsing Physics by Author "ADEENA FATIMA"

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    Photocatalytic degradation of Methyl Green dye mediated by pure and Mn-doped Zinc Oxide nanoflakes under solar light irradiation
    (UMT, Lahore, 2021) ADEENA FATIMA
    ABSTRACT Water pollution crises, which humanity is facing as a result of the rapid industrial revolution, increasing urbanization, and a burgeoning human population, necessitate a highly efficient, economical, easily accessible, eco-friendly, and long-term green solution to support the sustainable development of smart cities. The most significant source of water pollution is the extensive discharge of untreated industrial wastewater, especially when it is primarily made up of synthetic organic dyes (diazo and cationic dyes). Herein this study, pure and Mn-doped ZnO (2 wt.%) nanoparticles have been synthesized using the chemical precipitation method and characterized for photodegradation of methyl green pollutant dye. The structural analysis via XRD patterns has revealed that both intrinsic and Mn-doped ZnO (2 wt.%) samples have hexagonal wurtzite structure with appropriate phase, clearly indicating the absence of any impurity. The incorporation of manganese in the host ZnO lattice has decreased the crystallite size (21.10 → 18.76 nm) and Nano flakes type features with sizes in the 50 – 100 nm range have been observed through FESEM based surface morphological studies, both observations have merit in providing more active area and high surface area to volume ratio for photocatalytic reaction. The investigation of photophysical properties indicates that in Mn-doped ZnO nanoparticles, the absorption peak is blue-shifted by 5 nm (365 → 360 nm), due to the widening of the bandgap. The photocatalytic activities of the as-synthesized pure and Mn-doped ZnO photocatalysts have been evaluated by the degradation of MG pollutant dye in aqueous solutions under natural sunlight. The degradation of MG dye the photocatalysts follow the pseudo-first-order kinetics with relatively quasi-linear regression coefficient. Specifically, the efficiency has been calculated to be 62.78% for pure ZnO and 66.44% for Mn-doped–ZnO (2 wt. %) under 60 minutes sunlight irradiation. The rate of photocatalytic reaction (K) ~ 0.01477 min-1 and R2 ~ 0.92164 has been achieved for pure ZnO, whereas slightly higher ~ 0.01617 min-1 and R2 ~ 0.93494 has been observed for Mn-doped ZnO, respectively. Conclusively, the synergistic interactions with multiple charge transfer pathways, improvement of e−/h+ pair charge separation and efficient generation of hydroxyl radicals are supposed to be responsible for the high efficient photocatalytic activity of the Mn–doped ZnO photocatalyst for MG dye.